Hydraulic shock absorber



M. FIELDMAN I 1,991,201

HYDRAULI C SHOCK ABSORBER Filed July 7, 1950 3 Sheets-Sheet l Feb. 12, 1935.

M. FIELDMAN 1,991,201

HYDRAULIC sHocK ABsoRBEn I Filled July '7, 1930 Sheets-Sheet 2 fuiven/21021'- /yz'cae/@ 707/22 azz M. -FIELDMAN y HYDRAULIC SHOCK ABSORBER Filed July '7, 1930 5 Sheets-Sheet 5 Feb.12, 1935.

y" "UNITED i STATES `Patented Feb. `12,119.35

PATENTO'FFICE),

i nYDRAULro snoer: snsomsnng Michael rielaman, Philadelphia, `ra., assignorgby direct and mesne assignments, to 'Houde Engineering Corporation; Buffalo,

YNAZ., a4 corpora--` Appnummy, `193o,seria1 No. 166,319V 19 claims. (01188-139) This `invention relates to shock absorbersyand A more particularly to shock absorbers of the oscil- 1 latory type.

An important object of thepresent inventionis Ato provide in a shock absorber' of `this character a construction such that the shock absorber may be very readily and cheaply, produced ,and at-the same time may operate in such fashion4 that during normal movements of the vehicle frame lwith relation tol the axles orA such movements asare` occasioned `by slight road roughness, or side sway of the vehicle; theabsorber exercises a predeterf` mined low resistance eiect and when the relative movement becomes violent eitherasaresult of droppingoi the vehicle wheels into a depressionin the road and the` following body fall, or ameetl.- Aing of these wheels with an obstruction; andthe following rebound as a result of 'compression of 4the spr in`gs,ithe` resistance pressure increases sharply after a predetermined relative movement.

of the axles and frame to check such movement `and remains substantially constant duringthe major portion of the rebound or falling action fol;- lowing thefinitial relative vmovement so that such movements are checked andthe relative posii tions of the frameand` axles rapidly restored.`

A still further object ofQ the invention isito provide an oscillatory shockL absorber wherein the i pressure control, during movement oi the oscil- 30` latory piston in either direction, is the function of a metering groove backed by `a pressure controlling valve,` the metering groove .and 'pressurebacked valve as set forth in my prior application led July2'7,` 1929, Serial No. 381,512, withithfe additional .feature that the effective area of `the metering groove is varied throughout the distance through which the pistonmovesl and during .excessive `movements is reduced tozero so that Awherein,for the purpose of illustration, I have" shown preferredvembodimentsofmy invention` a desired maximum. pressure may be built' up.

A still `further object of the invention is the provision of a construction of` this, character in i which the arrangement is such that the metering period of oscillation of the piston.

These and other objects I attainy by theconstruction shown inithe` accompanying drawings grooves may bemade effective `tilfiroughja .desired y and wherein:

Fig. 1 is an inner cover plate being removed; I i. Fig. 2 isa section on line 2-12 "of Fig. 1; .5 Fig. 2a is an enlargement of a portion `of Figa,

illustratingbcertain leakagecollection grooves; t, K

iace view o f a shock absorber i constructed in accordance with my inventiomithe Fig. 3 isa section on line 3-43 of Fig. 2;j Fig`. 4 is asectionon line 1 -'4.0i Fig. 3;

Fig. 5 is ai chart showing a en meten ne fie*- l velopment of pressures in a shock absorber of `this .character Fig. 6 isa view similar to Fig.bx1 "showinga modi? i ,fied form of, the invention; 3i i i Fig. 7 isa section on lineJlA-'Z of Fig. 6; ,Fig 8 is a section onV line8-8 of Fig. "7; ,n Fig'. .9jis a vertical sectional viewthrough' a still further modified formof the invention;

Fig. 11 is a section online 1`1`11 of Fig."9. Referring now to ticularly to'Figs. 1 to 4'th`e`reof, thenumeral 10 the" drawings, and more par- Fig. l0 is a section on line`10U-l10 ofFig. 9j; and

generally vdesignatesffa'v cupshaped casing,l the'` bottom'` wall 11 of which' has a central opening 12 i which 'is extended through a tubular boss 13.` The f diameter of the bore of the boss .is increased.` at 1,4 4rior, a purpose presently to appear. In the `same-plane as the inner Vend of the boss, the bore` of the casing is enlarged at 15,'jthu'siaiording a `shoulder providing av seat forth'e outer edge of la plate 16,' the inner edge of which seats uponii the inner ,endoftheboss 13 and serves to subworking chambers 17 'and 18.` The circumferentialwall of the working chamber is preferably dened by finishing` 19fwh1ch bushing is ccnstructed in accordance with the directionsof my divide the vinterior `of the casing into'storage and `prior 1application filed December. 17, 1929, Serial .1

No. 414,726, for. Hydraulic shocklabsorbers, so that ,circumferential leakage collectieny grooves 20 and` 21 areprovidedwhich grooves arewn` communi-` cation through a` port 22 and noi-.chr23-formed in the plate 16 withthe storage chamber 17.

Located within thefworking chamber lare a stationary.y partition 24 and anoscillating piston 25, this piston havinga shaft`126 `which projects throughthe central opening of theplate 16 `and `for ashort distance. Inwardly ofthe innerzendlof each groove `thepartition element isprovided with a vertically-extendingbore l31, the upper end of which communicateswith a :pocket 32 at present .shown as vproduced by recessingythe sideyfaces of the partitionelement through the opening v'12" to, thelexteriorof the in the process of manufacture thereof. Communicating With each pocket 32 are a pair of bores 33 and 34, the outer ends of which are each enlarged and each open through an end tace 29 and have seated therein an apertured plug 35. 'I'he bores 33 and 34 communicating With one pocket 32 are disposed in opposite relation with those communicating With the other pocket.

Thus, one bore 33 leads from one face 29 to ay pocket 32 While the other bore leads from the other face 29 to the other pocket .32. The inner end of each bore 33 is formed as a valve seat for co-action with a valve 36 which .is maintained against its seat through a spring 37 extending between the plug and valve. Within each -bore 34 there is a valve 38 seating against the plug 35 to close the aperture thereof, this valve Y,being held against its seat by a spring 39. Spring 37 is a pressure-regulating spring for determining the normal l.minimum pressure at which the shock absorber may .operate'while spring 39 is .of higher pressure and seats its valve v38 against all ibut y excessive pressures in the shock` absorber. The

port series each including the port 31, a-poc'ket 32 and ports 33 `and 34 are spaced transversely of the partition element. The partition element is locked ,againstv rotation with relation to plate 16 as at 40land against rotation' with relation to casing 1'0 as` at `41. formed therein circumferentially#extending `grooves 42eachof which varies in depth from .end to endand each of Which Whenv the piston is in its normal or intermediate positionjhas its infner end justV communicating with the associated port 131 and its outer end overlapping the associated recess'SOor a considerable distance.l 'Variation in the cross sectionalarea .of grooves 42 rmay be accomplished in .any one of a number .of manners, in the presentinstance the groove "is .shown .asrouted .and as having vits 'base extending .chordlyso 'that the greatest cross sectional Y,area of .the groove occurs at the center thereof.

In operation of ashock absorber .of this character if Ynudi/.ement of thepiston from its normal vrposition toward either ofthe end faces ,29,15 relativelyslow .sol that the fluid ldisplaced.by .the reduction of the pressure chamber 43 at either side of ,the piston .may pass through the erfectiveiportion .of groove 42 Without, creating ,a greater presu :sure than'that necessary A'to .unseat valve -36 .against .the actionof its spring I3,3 then "the presysures `built up' Within the .shock Yabsorber are.

substantially .those indicated by the graph "line v A of .the-.chartl .of Eig.. 5.' Assuming `that .the movement .of the piston` is .morerapid `so that an .increase in .pressure isnecessary for .delivering of .the Vdisplaced fluid .beyond that `necessary ,to .unseat valve 3.6 but thatA the piston movement ,is un.- .isumcient .toshift lthe eifectivegroove .42 to .a .position where .it .doeslnot remain ,in lovevrl'apping .reflationto the recess .30 ,of the ,.partition, .then .the

1 .pressures built yup will be substantially represented -by the v'graph vline By of this figure. With-a .StiIlIurther increase in speed of rvmovement and "in ,theidistance through -Whichl the piston moves, "the movement-of the fpiston .carries fthe'outer end lofthe operative groove 42 lbeyond the tinner'iend tof 'thezassociated yrecess 3.9. `Until this occurs, fthe lpressures built 11p lin .the shock 1 absorber are only `those required `fordisplacement L.of `the ffluid through lthe metering groove 42 and Aithe valve port. After it occurs, -hovveventhere fis ino'outlet 'for iluid vfrom `the effective pressure chamber-to the other Aof the pressure chambers which Aat this comes the effective control.

The piston hub 28 has time might be referred to as a low pressure chamvious that the springs 37 constitute the means for determiningthe minimum Working pressure existing in the shock absorber duringl casual movements of the piston While the metering groove 42 constitutes a means for determining the :built-up A.pressures during rapid movements of the piston until these pressures reach a-prede- .termined value,at Which time the spring `39 be- It wiu be noted that :because the grooves 42 are spaced longi tudinally of the axis of the piston these grooves can beconstructed overlapping relation at their inner ends, thus enabling a metering groove of considerable length to be provided in the/hub Which'is built -w-ith -maximumr-and minimum radii as set vforth-many prior application vfiled f June 23, i927, Serial No. 200,812,-thus enabling thenishing Iof the hub by an inexpensive broaching operation. l

-In theconstruction shown in Figs. 6, 7 and 8, while thegeneral structure of the shock absorber is identical -W-ith that previously described, the metering grooves `and pressure valves are transfer-red from the hub of the piston and the staltionaryparti-tion to a -Wall of `the Working compartment 48a' and tothe piston 25a respectively. 'inthe structure shown in these iigures the inner -face of the plate 16 is abutted -by Va thin plate 44 Aagainst Which'the bushing 19a, forming 4the outer Wall of the -Working compartment, seats. The partition element 24a is provided with pockets 32 and with safety -vaive mechanism 45 corresponding to 'that previously described communicating 'with these pockets and each'l opening =through one-end Yface of the partition. -Each pocket is communication -with the opposite andra-ce 'of the partition element Vthrough a port 46. (The piston 25a is formed With transverselyextending ports 47, each opening through one Side rface of the piston and each formedjto pro- .l videa vail-ve seat 48 against which is springseated a pressure-regulating valve L49. vllach port 47 inthenormal position of the piston' communicates with the inner end of a metering `groove'WiSO at present shown'as constructed by slotting the `thin plate 44 hereinbefore mentioned with -an arcuate slot tapering from end'to end. Each-port 47 aft its'inner end communicates With Ia Vport 5-1 openingthrough the rear face of'the piston as regards the V,directionin which the asso- --c`iated metering groover'O extends, these `ports I'51 being `each shown as partially fformed'by. recessing-thepiston at 5 2. `It will vbe noted thatthe A-recesses-52 are-formed at the opposite face of the piston `from that at which the associatedports 47 open so that the sideffaces of the piston in 1 alignment with eachy groove present an unbroken surface. This is important as the efecf 'tive 'length of `the metering groovesl 50 may not be greater than the unbroken surface presented l by the piston in alignment therewith.

y'Operation of a shockgabsorber of this construc tion is identical 'with Vthe operation previously "described, 1

In ythe form of ,the invention shown in Figs. .9

to 11, the effective area ofthe metering groove "I Cil isfvaive-contrnld. In this structure .th-*general arrangement is that ofthe formshownin Figs. l'to 4. The partition element 24band piston 25h, howeven-areof modiledconstruction; The partition element 24h 'is formed-with arpair of ports 53 connectingltheend faces: 29.. thereof,

`these portsleach having one end thereof enlarged at .54 and having I,the inner end' of the` enlargement formed as fa' seat for the valve. `55 `maine tained against its` seat .by a pressure-regulating spring 56. Each port 53 adjacent theiinner `end ofl the enlargement and in' the smaller portion ofthe port is interruptedby a substantially` radial bore,57 within which `is arranged a piston valve58 `urged inwardly `by a spring 5 9.,f The inner endof the piston valve58 abuts" a` ballf 60 operating in a groove 61 formed in the hub of the piston 25h, this groove varying in depthl from s end `to end so that as the" piston oscillates the `valvel is shifted longitudinally ofthe bore and tends to open o r close the port y63andthus provide the variable metering `port necessary to production ofthe desiredtype'of operation hereinbefore described. Since the portsf53fare` transverselyv spaced in the partition element, the cam grooves 61 controlling the action of the pistonvalve `58 may be made to overlap and the` same general advantages may, accordingly, be obtained as are obtained by the structure shown in Figs. 1 to 4. The constructionshown in these figures, furthermore, illustrates the fact that it is not necessary that two relief valves be employed and that it is not necessary to mount these relief valves in the partition element. In` `this construction the piston is provided `with an axial? bore 62 communicating with transversely-spaced radial ports 63 and 64 opening through opposite` sides of the piston.. Between these ports a spring-seated relief valve 65 controls the flow and permits flow inyonly one` direction so that there is no relief for excessive pressures during movement of the piston in one direction. Where a single relief valve is provided, it will be provided so that it affords the relief during piston movements resulting from operation of the springs.

It will be obvious that where two relief valves are* employed,` springs of different pressure may be associated with these valves so that `the relief valves will act at different pressures.

From the foregoing it will be obvious that a shock absorber including the desired characteristics and of the oscillating type may be produced in a number of different fashions without in any manner departing from my invention and I, accordingly, do not limit myself to the specic arrangement hereinbefore set forth except as hereinafter claimed.`

`I claim: i

1. In ashock absorber, a casingr providing a working chamber, apartition i element in the chamber, an oscillatory piston likewise in the` chamber and combining with` the partitioning element to subdivide` the chamber into pressure compartments, a pair of uid transfer connections constituting the sole means of communication between saidcompartments at pressures below a predetermined safety relief pressure and eachincluding a metering port varying in cross sectional area as the piston oscillates, and a spring-seated, pressure-regulating check-valve controlling flow through each connection after `passage of iiuid through "said, metering port.

2. In ashock absorber, a casingproviding` a working chamber, `a partitionelement in the chamber, an oscillatory piston likewise in the chamber/andicombiningwiththe partitioning eleel 1 ment toisubdividefthe chambervinto pressure i.

compartments, fluid transfer connections consti- `tuting the sole means of f communication between said icompartinents atrpressres below apredetermined safety-relief pressure and each including ametering port `varying in cross'sectional area as the piston oscillates and closing afterv voscillation of thepiston'fromvits normal `position vthrougha predetermined '.fdistancegand a spring-seated,

pressure-regulating-l check-valve controlling iiow througheachconnection after passage of fluid through said metering port." i 1 f1 :aan device-ashamed inzciaimd wherein means are`provided-forivaryingthefcross/sectional area ofthe metering 'port'comprising a valve, and piston-actuatdmean's for shifting said valve.

14; A device as claimed'in claim 2 Vwherein'means areiprovided for varyingthe` cross sectional area of the metering portfcornprising a valve, and piston-actuated means Yfor shifting" said valve. t l

5."` A deviceasfclaimed clairnfl whereinthe" `connections `are formed" the `partition anda piston cammed valve is associated with each conn'ection` to -vary the f effective farea'lof i. a lportion thereof and thereby` provide? the metering port.

6. A device as claimed in `claim 2 wherein the connections are formed Ain the` partition anda piston cammed Valve is associated with each connection to vary the effective area of a portion thereof` and thereby provide the metering port.

7; A device as claimed in claim 1, wherein the connections are formed in the lpiston andthe metering ports include grooves formed in the vWalls of the working chamber.` j t ling flow through each connection after passage of fluid through said metering port.

10. In a shock absorber, a casing providing `a working chamber, Va partition element in the chamber, an oscillatory piston `likewise in ther chamber and combining with the partitioning element to subdivide the chamberinto pressure compartments, fluid transfer connections constituting the sole `means of` communication between saidcompartments and eachiincluding a metering port varying in cross sectional area as the piston oscillates and vclosing iafter oscillation of the piston from' its normal, position through a 8. A device` as claimed claim 2 wherein the i predetermined distance,` and a spring-seated, 'l

pressure-regulating check-valve controlling `flow through each connection after passage of fluid through said metering port. t

11. In a shock absorber a casing providing a4 working chamber, an oscillatory piston dividing `the chamber into a pair of pressure compartments, a fluid transfer connection providing ,com-

`munication between said compartments and including a metering port vvarying in'cross-sectionalV area as the piston oscillates, said transfer `connection comprising aductfformed in the pis- 1 wall of the partition element.

tongand'. afgroovje: cooperating, therewith and formed in; a Wall of the working chamber, anda spring seated pressurev regulating valve controle ling flow throughtheduct.` f l ,Y f 12.` A device `as claimed in claim 9' whereinthe metering ports are spaced longitudinally of, the piston axis and the means,v controlling the effective. area of the. meteringy porty include groovesv in thev piston hub which are similarlyl spaced and have their ends in overlapping relation.

13. A device asA claimed` in claim 10. wherein the metering. POrts are spaced longitudinallyof the piston axis and the means controllingrthe effective area ofithe metering portinelude: grooves Q in theI piston huh which aresimilarlyspacedand have their ends in overlapping relation.

14. A device as claimed in claim 9 .wherein the metering port is formed by co-action of agroove in the huleA of the piston with the yconfronting 15. A device as claimed in claim l-Ctwherein the metering; portV isformed by coaction of `a groove in the hubof the piston Withthe confronting Wall of the partition` element. Y

16. A device as claimed. in claimg wherein the elements. e

metering ports; areiormed by- -eo-action with grooves formed in thehub of the piston With the confronting Wall .ofv thepartition element and saicl,v groovesr arespaced 'longitudinally of the axis of ,thepiston.;l 1, f .Y

s 1'1; A deviceias claimed in claim 10 whereinthe -.metering ports aref` formed by co-actiorr with rneteringports. are formedfvb'y zo-action of grooves formedinone of. confronting faces of the piston hub andpartition Vandino-action of said grooves withgthe confrontingvfaceof the other of said t MICHAELLIE'LDMAN. 25 

